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Crisis in global oceans as populations of marine species halve in size since 1970

16 September 2015

Many species essential to commercial and subsistence fishing - and therefore global food supply - are significantly depleted due to over fishing. Global population sizes of the Scombridae family of food fish that includes tunas, mackerels and bonitos have fallen by 74 per cent. Declining stocks of bluefin and yellowfin are of particular concern. Some species found in UK waters, including the vulnerable porbeagle shark and the critically endangered leatherback turtle, have also undergone precipitous declines.

While over-exploitation is identified as the major threat to ocean biodiversity, the study finds that climate change is causing the ocean to change more rapidly than at any other point in millions of years. Rising temperatures and increasing acidity levels caused by carbon dioxide are further weakening a system that is already severely degraded through overfishing, habitat degradation and pollution.

Louise Heaps, Chief Advisor on Marine Policy at WWF-UK said:

As well as being a source of extraordinary natural beauty and wonder, healthy seas are the bedrock of a functioning global economy. By over-exploiting fisheries, degrading coastal habitats and not addressing global warming, we are sowing the seeds of ecological and economic catastrophe.

"But there are clear steps that all governments can take to restore our oceans. Creating networks of well-managed Marine Protected Areas is a proven way to enable wildlife and habitats to recover. Pushing for a strong global deal on climate change would help the seas sustain life far into the future. Taking serious steps to implement this year's Sustainable Development Goals in the UK and abroad could help build a global economy that values natural capital, respects natural habitats and rewards responsible business.

"Every one of us can take meaningful action, starting today, by ensuring that all the seafood we eat is responsibly sourced and Marine Stewardship Council accredited. And as ocean stakeholders, we can call for governments and the private sector to invest in the recovery of our ocean so that we can benefit in the long-term from what it has to offer."

The analysis tracked 5,829 populations of 1,234 species, from sea birds to sharks to leatherback turtles, making the data sets almost twice as large as past studies.

The report also shows steep worldwide declines in the cover of coral reefs, mangroves and seagrasses that support fish species and provide valuable services to people. It is very possible that we could lose coral reefs from most areas by 2050 as a result of climate change. With over 25 per cent of all marine species living in coral reefs and about 850 million people directly benefiting from their economic, social and cultural services, the loss of these reefs would be catastrophic.

Marco Lambertini, Director General of WWF International said:

"In the space of a single generation, human activity has severely damaged the ocean by catching fish faster than they can reproduce while also destroying their nurseries. Profound changes are needed to ensure abundant ocean life for future generations."

"We are in a race to catch fish that could end with people starved of a vital food source and an essential economic engine. Overfishing, destruction of marine habitats and climate change have dire consequences for the entire human population, with the poorest communities that rely on the sea getting hit fastest and hardest. The collapse of ocean ecosystems could trigger serious economic decline - and undermine our fight to eradicate poverty and malnutrition."

The findings are based on the Living Planet Index, a database maintained and analysed by researchers at the Zoological Society of London (ZSL). Following alarming statistics raised in WWF's Living Planet Report 2014, revealing huge declines in vertebrate populations around the world, this special report studies how overfishing, damage to habitat and climate change are affecting marine biodiversity.

Professor Ken Norris, Director of Science at ZSL said:

"The ocean works hard in the background to keep us alive, generating half of the world's oxygen and absorbing almost a third of the carbon dioxide produced from burning fossil fuels. It also feeds billions of people around the globe, some of whom rely solely on the oceans to survive. These devastating figures reveal how quickly human beings are changing the wildlife in our oceans and are a stark warning of the problems we might face as a result."

It's not all bad news in the UK. Recent assessments from the North Sea have shown that just over 50% of assessed stocks, including herring and haddock are being fished sustainably. Progress is being made in the designation of Marine Protected Areas, but the UK Government must do more to ensure delivery of a coherent and well-managed network of sites. Scotland has recently set a good example by proposing management measures that should ensure proper protection of sites.

Current gaps in the network in England include seagrass sites - home to two species of seahorse - and protection for mobile species such as sharks, skates and rays, which are identified as being in trouble on a global scale in this report.

· Threats to the ocean risk the loss of an annual economic output of at least US$2.5 trillion and an overall asset base of at least $24 trillion, as illustrated by a previous WWF study

· Earlier this year, WWF revealed that every dollar invested to create marine protected areas could yield triple the benefits through factors including employment, coastal protection, and fisheries. That analysis showed that increased protection of critical habitats could result in net benefits of between US$490 billion and US$920 billion accruing over the period 2015-2050.

· Nearly 3 billion people rely on marine and freshwater fish as a major source of protein. 12% global the population rely on fisheries as a livelihood, and 60% of world's population live within 100km of the coast.

Status of populations and habitats - examples from Living Blue Planet

Species / Habitat

Status

ALL MARINE SPECIES

Trends in 5,829 populations of 1,234 species

.49% decline in marine species populations between 1970 and 2012.

FISH

Trends in 930 species & 1463 populations

.50% reduction in population numbers globally between 1970 and 2010.

.29% of commercial fish stocks are now classed as overexploited and 61% as fully exploited.

SCOMBRIDAE

Incl. mackerels, tuna and bonitos

Trends in 58 populations and 17 species.

.74% decline between 1970 and 2010.

SEA CUCUMBERS

Massive overfishing in last 25 years. Harvested and traded in more than 70 countries.

.In the Galapagos, 98% decline in populations between 1993 and 2004 due to overfishing.

SHARKS & RAYS

Global catches have increased by 300% - but much is IUU so likely to be higher.

.25% of shark, rays and skates are now threatened with local extinction.

MARINE TURTLES

.Of 7 sub-populations of leatherbacks, 4 are critically endangered.

CORAL REEFS

.25% of all marine species live on coral reefs, although they cover <1% of the ocean.

.850 million people live within 100km of a coral reef.

.75% of the world's coral reefs are currently threatened.

.Coral reef cover - has decreased by more than 50% over the last 30 years.

.At current projected levels of ocean warming and acidification, there is mounting concern that coral reefs could be lost from most areas by 2050.

REEF FISH SPECIES

352 species and 2501 populations

.34% decline between 1979 and 2010.

SEAGRASS

Store 83,000 t of carbon / km2, more than double terrestrial forests.

.30% decline in cover over the last century.

.Possibly 51,000Km2 lost since 1879, 29% of the seagrass area.

FISH POPNS FOUND ON SEAGRASS

350 populations and 232 species

Pollution particular threat.

.70% decline between 1970 and 2010.

MANGROVES

.20% loss in mangrove cover between 1980 and 2005 = 3.6 million hectares.

.Rate of loss is 3-5X greater than average global forest loss.

DEEP SEA FISH

77 populations of 25 species.

.>40% of the world's fishing grounds are now in waters deeper than 200 m.

.Bottom trawling is happening at depths of up to 2000 m.

.72% decline over the last 40 years in the North Atlantic.

.Ross Sea toothfish, 50% decline of original stock biomass.

.Most deep sea fisheries are considered to be unsustainable.

About WWF
WWF is one of the world's largest and most respected independent conservation organizations, with over 5 million supporters and a global network active in over 100 countries. WWF's mission is to stop the degradation of the Earth's natural environment and to build a future in which humans live in harmony with nature, by conserving the world's biological diversity, ensuring that the use of renewable natural resources is sustainable, and promoting the reduction of pollution and wasteful consumption. www.panda.org/news for latest news and media resources

About ZSL
Founded in 1826, the Zoological Society of London (ZSL) is an international scientific, conservation and educational charity whose mission is to promote and achieve the worldwide conservation n of animals and their habitats. Our mission is realised through our ground-breaking science, our active conservation projects in more than 50 countries and our two Zoos, ZSL London Zoo and ZSL Whipsnade Zoo. For more information visit www.zsl.org